The present invention relates to an apparatus for decurling an advancing sheet, comprising at least one endless carrying belt, and multiple rollers for guiding the carrying belt, said multiple rollers including a decurling roller, wherein the mutual orientation between the carrying belt and the decurling roller is adjustable. The present invention also relates to a printing device containing such an apparatus.
In (electrophotographic) printing devices, a powder image is formed on a photoconductive member which is subsequently transferred to a sheet of support material. The sheet of support material is then heated to permanently affix the powder image thereto. As the sheet of support material passes through the various processing stations in the printing device, a curl or bend is frequently created therein. Occasionally, this curl or bend may be inherent in the sheet of support material due to the method of manufacture thereof. Frequently, a decurling apparatus is used to reduce paper curl in the process direction, said decurling apparatus commonly containing belts entrained by rollers, wherein one decurling roller is mounted between two fixed rollers, said decurling roller being adjustable with respect to the belt to enable adjustment of the decurling capacity of the decurling apparatus. Adjustment of the mutual orientation of the belt and the adjustable decurling roller, and hence of the decurling capacity of the decurling apparatus, leads to a change of direction of a belt span entrained between the decurling roller and the fixed roller positioned downstream the decurling roller, thereby leading to a change of the discharge direction of the sheets out of the decurling apparatus. However, this change of discharge direction often leads to adverse forced head-on contact of the decurled sheet with a receiving tray, as a result of which the decurling effect of the decurling apparatus is commonly counteracted as an undesired new curl will be induced in the sheet.